Because organosilicon polymers that contain the silalkylenesiloxane unit with the general formula ##STR3## in which R=monovalent hydrocarbon group
a=positive integer
are less susceptible to molecular chain scission by ionic substances (e.g., acids, alkalis, and so forth) than are diorganopolysiloxanes, such silalkylenesiloxane unit-containing organosilicon polymers are currently under investigation for utilization in various specialized applications. The ring-opening polymerization of cyclic silalkylenesiloxane is known for the synthesis of said silalkylenesiloxane unit-containing organosilicon polymers (refer to Japanese Laid Open Patent Application Numbers Hei 4-65428 and Hei 4-65429 and Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, 739-744, April, 1971) .
The method for synthesizing this organosilicon polymer that is taught in Japanese Laid Open Patent Application Numbers Hei 4-65428 and Hei 4-65429 and in the article in Izvestiya Akademii Nauk SSSR requires the preliminary synthesis of a cyclic silalkylenesiloxane such as 2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane. However, these cyclic silalkylenesiloxanes are typically themselves quite difficult to synthesize. Moreover, as reported in the article in Izvestiya Akademii Nauk SSSR, a partial depolymerization of the polysilalkylenesiloxane occurs in this method, which leads to a substantial reduction in the yield of the organosilicon polymer.